A typical motor vehicle driven by an internal combustion engine comprises, in addition to the engine, a fuel filter which can have a fuel filter housing of a synthetic resin material or plastic and a replaceable filter cartridge. The fuel supply system can additionally comprise a fuel pump, a fuel tank and a fuel line for delivering the fuel via the pump to the internal combustion engine.
The engine system can also comprise an air-supply system for delivering the combustion air to the engine. The air-supply system can comprise an air filter and an air duct. The fuel filter housing is traversed by the fuel under the pressure of the pump and, when the pump is energized or switched in, the fuel filter housing is under a superatmospheric pressure.
The vehicle may be provided with a tank-venting system for drawing fuel vapor out of the tank. In that case the air-supply system will, for the purposes of this application, be understood to also include the components of the tank-venting system. The term "system" is used herein to refer to all of the components provided for tank venting, air supply and fuel supply according to the invention.
In the past the fuel filter has been provided along the fuel line in a housing connected on one side to the fuel line and on the other side to the fuel injectors or carburetor. The housing was formed with a cover which could be removed to enable replacement of the filter cartridge.
For safety purposes and to avoid contamination of the environment, the filter housing had to be secure against leakage and diffusion resistant so that the fuel, which is a mixture of organic compounds like the synthetic resin housing, would not leak or diffuse through the housing and escape into the environment. From a practical point of view both the leakage rate and the diffusion rate should be ideally zero. To accomplish this, in the past, the housing had to be well sealed and of expensive construction. Fabrication was time-consuming and expensive and mounting of the fuel filter was likewise a problem. Special space had to be provided in the engine compartment of the vehicle to accommodate the filter and this was not always available. In the mounted position, the fuel filter was not always accessible readily and could not be opened and closed with absolute reliability. Security against leakage, both around the cover and by diffusion through the walls of the housing left much to be desired and decreased with time to the point that it did not satisfy modern needs, legal requirements or desires.